Acrylic adhesive composition and organoboron initiator system

ABSTRACT

A two-part initiator system useful in acrylic adhesive compositions comprising in one-part a stable organoboron amine complex and in the second part an organic acid destabilizer or activator. This initiator is particularly useful in elastomeric acrylic adhesive compositions and provides a fast, room temperature cure with good stability and exhibiting both high tensile strength and high peel strength.

This application is a division of application Ser. No. 07/692,766, filedApr. 29, 1991, U.S. Pat. No. 5,106,928.

BACKGROUND OF THE INVENTION

This invention relates to a novel organoboron complex initiator systemand an acrylic adhesive composition containing this initiator. Moreparticularly this invention involves a two-part initiator systemcomprising in one-part a stable organoboron amine complex and in thesecond part an organic acid destabilizer or activator. This initiatorsystem is especially useful in elastomeric acrylic adhesivecompositions.

Adhesive compositions including acrylic adhesives such as solutions ofelastomeric polymers in soluble polymerizable acrylic or methacrylicmonomers are well known in the art. These compositions which areespecially known for their toughening properties generally include aredox system which comprises a catalyst or initiator, an accelerator andan activator to initiate cure, as well as other additives such asadhesion promoters, chelators, cross-linking agents, thickeners andplasticizers. Two-part acrylic adhesives where an activator is added asa separate second component are widely used and are known for curingspeed as well as toughness. The catalyst or initiator typically used inthese adhesives are free-radical initiators of the organic peroxy orhydroperoxy type, perester or peracid type.

Many known adhesive systems, such as the epoxies, require a thermal cureto obtain desirable properties, while others that do not, usuallyrequire prolonged cure times. In comparison, the adhesive compositionwith organoboron amine complex initiator of this invention cures at roomtemperature and reaches high tensile strength in a short period of time.Additionally, the adhesive composition of this invention has shownexceptional stability on ageing while exhibiting both high tensilestrength and high peel strength.

SUMMARY OF THE INVENTION

This invention involves a novel two-part organoboron amine complexinitiating system useful in elastomeric acrylic adhesives compositionsto provide better and faster room temperature curing thereof.

The organoboron initiating system of this invention is a two-part systemcomprising:

A) a stabilized organoboron amine complex of the formula: ##STR1## whereR, R₁ and R₂ are alkyl of 1 to 10 carbon atoms or phenyl, R₃ and R₄ arehydrogen or alkyl of 1 to 10 carbon atoms, or ##STR2## where R₅ and R₆are hydrogen or alkyl of 1 to 10 carbon atoms, m is 2 to 10 and n is 1to 6, and

B) an organic acid activator having the formula:

    R--COOH

where R is hydrogen, alkyl or alkenyl of 1 to 8 carbon atoms, or arylhaving 6 to 10 carbon atoms.

DETAILED DESCRIPTION OF THE INVENTION

The stabilized organoboron amine complex of the structure (I) whichcomprises one part of the initiator of this invention is made bycombining an organoboron compound with a primary or secondary amine orpolyamine containing primary or secondary amines. The organoboroncompound has the formula: ##STR3## where R, R₁ and R₂ are alkyl of 1 to10 carbon atoms or phenyl, preferably alkyl of 1 to 4 carbons. In thisformula, the alkyl groups may be straight or branch chained and thephenyl group may contain substituents such as alkyl, alkoxy or halogen.Illustrative compounds of this type include, e.g., trimethylboron,triethylboron, tri-n-butylboron, tri-sec-butylboron andtri-isobutylboron.

The amine which is used in forming the organoboron amine complex (I) maybe any primary or secondary amine or polyamine containing a primary orsecondary amine, or ammonia and having the following formula: ##STR4##where R₃ and R₄ are hydrogen or alkyl of 1 to 10 carbon atoms, or##STR5## where R₅ and R₆ are hydrogen or alkyl of 1 to 10 carbon atoms,m is 2 to 10, and n is 1 to 6. The alkyl groups in this formula may bestraight or branch chained. Preferably, the R groups noted in the aminewill be hydrogen or alkyl of 1 to 4 carbon atoms, m will be 2 to 6 andmore preferably 2 to 3 and n will be 1 to 2. Illustrative compounds ofthis type include, e.g., n-octylamine, 1,6-diaminohexane, diethylamine,dibutylamine, diethylene triamine, dipropylene diamine, ammonia,1,3-propylenediamine and 1,2-propylenediamine.

The stabilized amine complex can be prepared by combining a solution ofthe organoboron with the amine under an inert atmosphere with cooling asneeded.

The activator used as the second part or component of the initiatorsystem will be a compound which will destabilize or liberate the freeorganoboron compound by removing the amine group and thereby allow it toinitiate the polymerization process. This activator is an organic acidhaving the formula:

    R--COOH

where R is H, alkyl or alkenyl of 1 to 8 and preferably 1 to 4 carbonatoms, or aryl of 6 to 10, preferably 6 to 8 carbon atoms. It is furtherunderstood that the alkyl or alkenyl group of this organic acid may bestraight or branch chained and the aryl may contain substituents such asalkyl, alkoxy or halogen. Illustrative examples of compounds of thistype include: acrylic acid, methacrylic acid, benzoic acid, andp-methoxybenzoic acid.

Generally the initiator system of this invention will comprise theorganoboron amine complex and an effective destabilizing amount of theorganic acid activator. More particularly from about 0.1:1 to 200:1parts by weight of acid to amine complex and preferably from about 1:1to 24:1 parts by weight of acid to amine complex may be used.

The organoboron initiator of this invention is particularly useful inacrylic adhesive compositions and especially solutions of elastomeric orrubber polymers in compatible polymerizable acrylic monomers.

The polymerizable acrylic monomer may be monofunctional, polyfunctionalor a combination thereof.

One class of polymerizable monomers useful in the present compositionscorrespond to the general formula: ##STR6## wherein R is selected fromthe group consisting of hydrogen methyl, ethyl, ##STR7## R' is selectedfrom the group consisting of hydrogen, chlorine, methyl and ethyl;

R" is selected from the group consisting of hydrogen, hydroxy, and##STR8## m is an integer equal to at least 1, e.g., from 1 to 8 orhigher and preferably from 1 to 4 inclusive;

n is an integer equal to at least 1, e.g., from 1 to 20 or more; and

p is one of the following: 0 or 1.

Monomers useful in this invention and which come within the abovegeneral formula include, for example, ethylene glycol dimethacrylate,ethylene glycol diacrylate, polyethylene glycol diacrylate,tetraethylene glycol dimethacrylate, diglycerol diacrylate, diethyleneglycol dimethacrylate, pentaerythritol triacrylate, trimethylolpropanetrimethacrylate, and other polyether diacrylates and dimethacrylates.

The above class of monomers is in essence described in U.S. Pat. No.3,043,820 issued Jul. 10, 1962 (to R. H. Krieble).

A second class of polymerizable monomers useful in the presentcompositions correspond to the general formula: ##STR9## wherein Rrepresents hydrogen, chlorine, methyl or ethyl; R' represents alkylenewith 2-6 carbon atoms; and, R" represents (CH₂)_(m) in which m is aninteger of from 0 to 8, or ##STR10## and n represents an integer of from1 to 4.

Typical monomers of this class include, for example, dimethacrylate ofbis(ethylene glycol) adipate, dimethacrylate of bis(ethylene glycol)maleate, dimethacrylate of bis(diethylene glycol) phthalate,dimethacrylate of bis(tetraethylene glycol) phthalate, dimethacrylate ofbis(tetraethylene glycol) sebacate, dimethacrylates of bis(tetraethyleneglycol) maleate, and the diacrylates and chloroacrylates correspondingto said dimethacrylates, and the like.

The above class of monomers is in essence described in U.S. Pat. No.3,457,212 issued Jul. 22, 1969 (Sumitomo Chemical Company, Ltd.)

Also useful herein are monomers which are isocyanate-hydroxyacrylate orisocyanate-aminoacrylate reaction products which may be characterized asacrylate terminated polyurethanes and polyureides or polyureas. Thesemonomers correspond to the general formula: ##STR11## wherein X isselected from the group consisting of --O-- and ##STR12## and R is amember selected from the group consisting of hydrogen and lower alkyl of1 to 7 carbon atoms; A represents the organic residue of an activehydrogen containing acrylic ester wherein the active hydrogen has beenremoved, the ester being hydroxy or amino substituted on the alkylportion thereof and the methyl, ethyl and chlorine homologs thereof; nis an integer from 1 to 6 inclusive; and B is a mono- or polyvalentorganic radical selected from the group consisting of alkyl, alkylene,alkenyl, cycloalkyl, cycloalkylene, aryl, aralkyl, alkaryl,poly(oxyalkylene), poly(carboalkoxyalkylene), and heterocyclic radicalsboth substituted and unsubstituted.

Typical monomers of this class include the reaction product of mono- orpolyisocyanate, for example, toluene diisocyanate, with an acrylateester containing a hydroxy or amino group in the non-acrylate portionthereof, for example, hydroxyethyl methacrylate.

The above class of monomers is in essence described in U.S. Pat. No.3,425,988 issued Feb. 4, 1969 (Loctite Corporation).

Another class of monomers useful in the present application are themono- and polyacrylate and methacrylate esters of bisphenol typecompounds. These monomers may be described by the formula: ##STR13##where R¹ is methyl, ethyl, carboxyalkyl or hydrogen; R² is hydrogen,methyl or ethyl; R³ is hydrogen, methyl or hydroxyl; R⁴ is hydrogen,chlorine, methyl or ethyl; and n is an integer having a value of 0 to 8.

Representative monomers of the above-described class include:dimethacrylate and diacrylate esters of 4,4'-bis-hydroxyethoxy-bisphenolA; dimethacrylate and diacrylate esters of bisphenol A; etc. Thesemonomers are essentially described in Japanese Patent Publication No.70-15640 (to Toho Chemical Manuf. Ltd.).

In addition to the monomers already described, other useful monomers aremonofunctional acrylate and methacrylate esters and the substitutedderivatives thereof such as hydroxy, amide, cyano, chloro, and silanederivatives. Such monomers include, for example, methyl acrylate, methylmethacrylate, ethyl acrylate, ethyl methacrylate, isobornylmethacrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate,hydroxypropyl methacrylate, butyl acrylate, n-octyl acrylate,2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, decylmethacrylate,dodecyl methacrylate, cyclohexyl methacrylate, tert-butyl methacrylate,acrylamide, N-methylolacrylamide, diacetone acrylamide, N-tert-butylacrylamide, N-tert-octyl acrylamide, N-butoxyacrylamide,gamma-methacryloxypropyl trimethoxysilane, 2-cyanoethyl acrylate,3-cyanopropyl acrylate, tetrahydrofurfuryl methacrylate,tetrahydrofurfuryl chloroacrylate, glycidyl acrylate, glycidylmethacrylate, and the like.

The monomers useful herein are seen to be polymerizable monomers havingone or more acrylic or substituted acrylic groups as a common, unifyingcharacteristic, and for convenience may be generically termed acrylicmonomers.

The elastomer or rubber polymers may be any of the typically availablesynthetic rubbers that are soluble in the monomer such as those based onpolyisoprenes, polybutadienes, polyolefins, polyurethane, polyesters,etc. Examples of elastomeric materials include homopolymers such aspolybutadiene, polyisoprene and polyisobutylene; diene type copolymerssuch as butadiene/styrene copolymer, butadiene/acrylonitrile copolymer,butadiene/methyl methacrylate copolymer and butadiene/alkyl acrylatecopolymer; ethylene/vinyl acetate copolymers; ethylene/alkyl acrylatecopolymers (1-8 carbons in the alkyl group), rubbery polyalkyl acrylatesor copolymers thereof; polyurethane; chlorinated polyethylenes; and EPDM(ethylene/propylene/diene terpolymers).

The elastomers of these structures may contain a functional group at oneor both ends or within a particular segment or repeating unit of thecopolymer. Among the suitable functional groups are vinyl, epoxy,carboxyalkyl, and mercapto groups. Other functional groups may beemployed as deemed useful as determined by routine experimentation.

One preferred group of elastomers are the block copolymers. Several suchblock copolymers are manufactured by Shell Chemical Company under thetradename Kraton and by Firestone under the tradename Stereon. Inparticular, Stereon 840A, a poly(styrene-b-butadiene-b-styrene) blockcopolymer, has been found to be especially useful in the instantadhesive composition. Other preferred block copolymers of this type areavailable under the tradename Solprene 416, manufactured by PhillipsPetroleum Co.

The monomer solution containing the elastomer or rubbery polymer iscommonly prepared by dissolving the elastomer in the monomer, which maybe in the form of a syrup. In some cases, the monomer solution may beprepared by extracting a rubbery polymer from a latex of the rubberypolymer in water, as used for suspension polymerization, and thendissolving in the monomer.

The amount of the acrylic monomer to be used in this invention may varysomewhat depending on the specific properties desired but generallyabout 10 to 90% by weight of the composition and preferably about 15 to80% by weight is used. Adjustment within these ranges are easily madewithin the skill of the art. The elastomer is generally present inamounts of about 5 to 80% by weight and preferably about 20 to 60% byweight of the composition.

The second part of the initiator which contains the acid activator,preferably may also contain a peroxy or hydroperoxy component having theformula:

    R--OOH

where R is hydrogen, alkyl of 1 to 10 preferably 4 to 10 carbon atoms oraryl or alkaryl of 6 to 14, preferably 6 to 10 carbon atoms.Illustrative compounds of this type are t-butyl hydroperoxide and cumenehydroperoxide. Typically these hydroperoxy compounds which aid in theinitiation of polymerization are used in the initiator system in amountsof about 0.2:1 to 100:1 and preferably from about 0.4:1 to 20:1 parts byweight of hydroperoxy to amine complex.

The organoboron amine complex used in an adhesive composition inaccordance with this invention generally comprises from about 0.1 to 5%by weight of the total composition and preferably from about 0.5 to 2.5%and the organic acid activator comprises from about 0.5 to 20%,preferably from about 1 to 12% by weight of the total composition. Whena hydroperoxy compound is used in the adhesive composition, it generallycomprises from about 0.2 to 10% by weight of the total composition andpreferably from about 0.5 to 2%.

Other additives useful in elastomeric acrylic adhesives of this type,such as adhesion promoters, chelators, cross-linking agents, inhibitors,activators such as N,N-dimethyltoluidine as well as thickeners,plasticizers and diluents may also be used in the adhesive compositionsof this invention.

The organoboron initiator system as described above comprises a twocomponent system. When used in the acrylic rubber compositions of thisinvention generally the two parts are mixed in equal quantities of themonomer-polymer solution, but this may vary at the discretion of theuser. That is, the stabilized organoboron compound is added to asolution of the elastomer or rubber polymer dissolved in thepolymerizable acrylic monomer and the organo acid activator and optionalhydroperoxy compound are added as a second part which also may be in asolution of the rubber polymer in acrylic monomer.

Adhesive compositions of this invention are particularly useful instructural and semi-structural applications such as speaker magnets,metal-metal bonding (automotive) glass-metal bonding, glass-glassbonding, circuit board component bonding, selected plastic to metal,glass, wood, etc. and electric motor magnets.

In the following examples, which are merely illustrative of theembodiments of this invention, all parts and percentages are given byweight and all temperatures are in degrees Celsius unless otherwisenoted.

EXAMPLE I Preparation of Organoboron Amine Complexes

Into a 3-neck flask containing a stirrer, condenser, thermometer and anitrogen purge, 11.1 g (0.15 m, 50% excess) of 1,3-propylene diamine wasadded and the nitrogen purge continued while 100 ml of 1 molar solution(0.1 m) of tributylboron in tetrahydrofuran was further added. A mildexotherm developed and the temperature was kept below about 40° C. bycooling as necessary. When the addition was complete, the mixture wasstirred for about 0.5 hour and transferred to a bottle previouslyflushed with nitrogen. This amine complex is identified below asinitiator XII as well as other amine complexes prepared in a similarmanner using the amines and amounts indicated.

    ______________________________________                                        AMINE          AMOUNT      INITIATOR NO.                                      ______________________________________                                        ethylene diamine                                                                             6.0 g (0.10 m)                                                                            I                                                  ethylene diamine                                                                             9.0 g (0.15 m)                                                                            II                                                 ethylene diamine                                                                             12.0 g (0.20 m)                                                                           III                                                1,2-propylene diamine                                                                        11.1 g (0.15 m)                                                                           IV                                                 n-octylamine   19.4 g (0.15 m)                                                                           V                                                  1,6-diaminohexane                                                                            17.4 g (0.15 m)                                                                           VI                                                 diethylenetriamine                                                                           10.3 g (0.10 m)                                                                           VII                                                1,3-propylene diamine.sup.1                                                                  7.4 g (0.10 m)                                                                            VIII                                               4-aminomethylpyridine                                                                        10.8 g (0.10 m)                                                                           IX                                                 3-aminomethylpyridine                                                                        10.8 g (0.10 m)                                                                           X                                                  diethylamine   10.95 g (0.15 m)                                                                          XI                                                 1,3-propylene diamine                                                                        11.1 g (0.15 m)                                                                           XII                                                ______________________________________                                         .sup.1 1 molar solution of triethylboron in tetrahydrofuran used         

EXAMPLE II Preparation of Adhesive Composition

An adhesive formulation was prepared consisting of two parts that weremixed just prior to use. The first part contained the monomer-polymersyrup and the stabilized organoboron amine complex initiator fromExample I. The second part contained a similar monomer-polymer syrup andan acid activator or reagent that destabilized the organoboron aminecomplex liberating the free organoboron. When mixed with the first partpolymerization was initiated. The two adhesive composition parts were:

    ______________________________________                                        Part I                                                                        Stereon 840A (styrene-butadiene block copolymer)                                                        30 parts                                            Isobornyl methacrylate    70 parts                                            Organoboron amine initiator No. 12.sup.1                                                                 4 parts                                            Part II                                                                       Stereon 840A              30 parts                                            Isobornyl methacrylate    61 parts                                            Methacrylic acid           5 parts                                            Cumene hydroperoxide (CHP)                                                                               4 parts                                            ______________________________________                                         .sup.1 1 molar solution in tetrahydrofuran                               

Approximately equal portions of Parts I and II were mixed and applied tosteel plates and allowed to cure. Tensile shear strength measurement onthe adhesive bond was made according to the ASTM standard methodD1002-72(1973) and found to be 2000 psi.

Additional adhesive formulations were prepared in a similar manner usingthe components as identified below along with the resulting tensilestrength determined is described above for the formed adhesive bond.

    __________________________________________________________________________             INITIATOR         BOND TENSILE                                       RUBBER (%)                                                                             (%)    % ACID.sup.1                                                                        % CHP.sup.2                                                                        STRENGTH PSI                                       __________________________________________________________________________    Stereon 840a (20)                                                                      XII (0.5)                                                                            10      0.1                                                                              1875                                               Stereon 840a (25)                                                                      VIII (0.5)                                                                            1    1    1550                                               Kraton 1107 (20).sup.3                                                                 II (0.5)                                                                             10    1    1850                                               Kraton 1107 (20)                                                                       II (0.25)                                                                            10    1    1350                                               Kraton 1107 (20)                                                                       II (1.0)                                                                             10    1    2100                                               Hycar 4051 (10).sup.4                                                                  IV (0.5)                                                                             10    1    1200                                               Kraton 1122 (25).sup.5                                                                 VI (0.5)                                                                              1    1    1500                                               Stereon 840A (20)                                                                      I (0.5)                                                                                0.5   1.7                                                                              1500                                                        also contains 13% octyl acrylate                                     Stereon 840A (30)                                                                      VIII (0.5)                                                                           10    1    2700                                                        monomer was tetrahydrofurfuryl methacrylate                          __________________________________________________________________________     .sup.1 methacrylic acid                                                       .sup.2 cumene hydroperoxide                                                   .sup.3 styreneisoprene                                                        .sup.4 polyacrylic rubber polymer                                             .sup.5 styreneisoprene                                                   

EXAMPLE III

Similar adhesive formulations were prepared as in Example II using anamine complex of 1,3 propylene diamine and triethyl boron as theinitiator (initiator No. VIII). The formulations contained two-parts asin Example II that were mixed just prior to use and had the followingcompositions:

    __________________________________________________________________________    Part I                                                                        Sample No.                                                                          Initiator                                                                          Rubber.sup.1                                                                       Monomer A                                                                            Monomer B                                                                            Monomer C                                       __________________________________________________________________________    3A-I  2 parts                                                                            25 parts                                                                           60 parts                                                                             15 parts                                                                             --                                                              (IBOMA)                                                                              (OMA)                                                  3B-I  2 parts                                                                            25 parts                                                                           60 parts                                                                             15 parts                                                                             --                                                              (IBOMA)                                                                              (OMA)                                                  3C-I  2 parts                                                                            25 parts                                                                           60 parts                                                                             15 parts                                                                             --                                                              (IBOMA)                                                                              (ODA)                                                  3D-I  2 parts                                                                            25 parts                                                                           60 parts                                                                             15 parts                                                                             --                                                              (IBOMA)                                                                              (HDDA)                                                 3E-I  2 parts                                                                            25 parts                                                                           60 parts                                                                             15 parts                                                                             --                                                              (IBOMA)                                                                              (HDDMA)                                                3F-I  2 parts                                                                            30 parts                                                                           --     --     70 parts                                                                      (THFMA)                                         3G-I  2 parts                                                                            30 parts                                                                           --     --     70 parts                                                                      (THFMA)                                         3H-I  2 parts                                                                            30 parts                                                                           --     --     70 parts                                                                      (THFMA)                                         3I-I  2 parts                                                                            30 parts                                                                           --     --     70 parts                                                                      (THFMA)                                         3J-I  2 parts                                                                            30 parts                                                                           55 parts                                                                             --     15 parts                                                        (IBOMA)       (HPMA)                                          __________________________________________________________________________

    __________________________________________________________________________    Part II                                                                       Sample No.                                                                          Rubber.sup.1                                                                        Monomer A                                                                            Monomer B                                                                            Acid CHP                                            __________________________________________________________________________    3A-II 25 parts                                                                            50 parts                                                                             15 parts                                                                             10 parts                                                                           --                                                         (THFMA)                                                                              (OMA)  (MAA)                                               3B-II 25 parts                                                                            50 parts                                                                             15 parts                                                                             10 parts                                                                           --                                                         (IBOMA)                                                                              (OMA)  (MAA)                                               3C-II 25 parts                                                                            50 parts                                                                             15 parts                                                                             10 parts                                                                           --                                                         (THFMA)                                                                              (ODA)  (MAA)                                               3D-II 25 parts                                                                            50 parts                                                                             15 parts                                                                             10 parts                                                                           --                                                         (THFMA)                                                                              (HDDA) (MAA)                                               3E-II 25 parts                                                                            50 parts                                                                             15 parts                                                                             10 parts                                                                           --                                                         (THFMA)                                                                              (HDDMA)                                                                              (MAA)                                               3F-II 30 parts                                                                            60 parts                                                                             --     10 parts                                                                           0.125 parts                                                (THFMA)       (MAA)                                               3G-II 30 parts                                                                            60 parts                                                                             --     10 parts                                                                           0.250 parts                                                (THFMA)       (MAA)                                               3H-II 30 parts                                                                            60 parts                                                                             --     10 parts                                                                            0.5 parts                                                 (THFMA)       (MAA)                                               3I-II 30 parts                                                                            60 parts                                                                             --     10 parts                                                                           1 part                                                     (THFMA)       (MAA)                                               3J-II 30 parts                                                                            55 parts                                                                             15 parts                                                                             1 part                                                                             --                                                         (THFMA)                                                                              (HPMA) (MAA)                                               __________________________________________________________________________     .sup.1 Stereon 840A                                                           IBOMA isobornyl methacrylate                                                  OMA 2-ethylhexyl methacrylate                                                 ODA n-octylacrylate/n-decylacrylate mixture                                   HDDA 1,6-hexanediol diacrylate                                                HDDMA 1,6-hexanediol dimethacrylate                                           THFMA tetrahydrofurfryl methacrylate                                          HPMA 2-hydroxypropyl methacrylate                                             MAA methacrylic acid                                                          CHP cumene hydroperoxide                                                 

Approximately equal portions of Parts I and II were applied to steelplates and allowed to cure at room temperature. The bonds were evaluatedfor tensile shear strength using ASTM standard method D1002-72 (1973) inpounds/inch² (psi) and for T-peel using ASTM standard method D1876-72 inpounds/linear inch (pli). These results are shown below (where, e.g., 3Ais 3AI+3AII).

    ______________________________________                                        Adhesive Sample No.                                                                           Tensile Shear (psi)                                                                         T-Peel (pli)                                    ______________________________________                                        3A              2500          20                                              3B              1700          8                                               3C              2400          14                                              3D              2700          6                                               3E              2900          5                                               3F              1875          --                                              3G              2600          --                                              3H              2000          --                                              3I              2600          --                                              3J              1800          4                                               ______________________________________                                    

What is claimed is:
 1. A two-part initiator composition comprising:A) astabilized organoboron amine complex of the formula: ##STR14## where R,R₁ and R₂ are alkyl of 1 to 10 carbon atoms or phenyl, R₃ and R₄ arehydrogen or alkyl of 1 to 10 carbon atoms, or ##STR15## where R₅ and R₆are hydrogen or alkyl of 1 to 10 carbon atoms, m is 2 to 10 and n is 1to 6, and B) an effective destabilizing amount of an organic acidactivator having the formula:

    R--COOH

where R is H, alkyl or alkenyl of 1 to 8 carbon atoms or aryl of 6 to 10carbon atoms.
 2. The composition of claim 1 wherein in the organoboronamine complex, R, R₁ and R₂ are alkyl of 1 to 4 carbons, R₃, R₄ and R₅are hydrogen or alkyl of 1 to 4 carbon atoms, R₆ is hydrogen, m is 2 to6 and n is 1 to
 2. 3. The composition of claim 2 wherein the R group ofthe organic acid of Part B is an alkyl or alkenyl group of 1 to 4carbons or an aryl of 6 to 8 carbons.
 4. The composition of claim 3wherein from about 0.1:1 to 200:1 parts by weight acid to amine complexare used.
 5. The composition of claim 4 wherein the second part B) alsocontains a hydroperoxy compound.
 6. The composition of claim 5 whereinthe hydroperoxy compound has the formula R--OOH, where R is hydrogen,alkyl of 1 to 10 carbon atoms or aryl or alkaryl of 6 to 14 carbonatoms.
 7. The composition of claim 5 wherein the complex is acombination of tributyl boron and ethylene diamine or propylene diamine.